As a multi chamber-type vacuum system, for example, a chemical vapor deposition (CVD) apparatus with chambers such as a loading and unloading chamber and a processing chamber that surround a transport apparatus which is arranged in the center thereof is known. The transport apparatus constituting such a CVD apparatus includes a stretchable robot arm, which has a robot hand at one end thereof to support a substrate (a transportation target).
Allowing the robot arm to be rotatable, makes it possible to transport the substrate between a plurality of such chambers, for example, by rotating the robot arm to guide the substrate from one to another of the chambers after extending the robot arm in the chamber to accept the substrate with the robot hand or withdrawing the robot arm to take out the substrate from the chamber.
In the related art, a configuration is known in which the presence of the substrate is detected using a light emitting and receiving element in such a transport apparatus to determine whether the substrate is mounted on the robot hand or not, the middle (center) of the substrate, for example, serving as a detection position (for example, refer to Patent Document 1).
However, in a configuration in which only one point (for example, the center) of the substrate serves as the detection position to detect the presence of the substrate, it is possible to detect the presence of the substrate on the robot hand but it is impossible to detect a more accurate state of the substrate, such as whether the substrate is supported at a predetermined position of the robot hand or not (position shift detection) and whether the substrate supported by the robot hand is damaged or not (damage detection).
Accordingly, a transport apparatus is known in which, for example, a plurality of detection positions are set on the substrate, and a plurality of detection units, such as the light emitting and receiving element, are provided toward the plurality of detection positions (for example, refer to Patent Document 2). In the transport apparatus, the robot hand has respective detection units for respective stop positions that face the respective chambers, the number of the detection units being equal to the number of the detection positions that are set. By setting the plurality of detection positions with respect to one substrate, it is possible to detect a shift in the position where the substrate is supported on the robot hand and to detect a defect in the substrate.
Specifically, for example, the detection positions are set as three points on a concentric circle of the substrate which are shifted by 120° each, and light (detection light) is applied toward the three-point detection positions at each of the stop positions that face the respective chambers, or a sensor is provided to receive the light. Therefore, for example, in a vacuum system including six chambers around the transport apparatus, three sensors are provided at each of six stop positions, and 18 sensors are provided in total.